Reduced-impact sliding pressure control valve for pneumatic hammer drill
| DWPI Title: Pneumatic hammer drill i.e. downhole hammer drill, for percussive drilling, has valve positioned over feed tube inside piston and defining forward and rear limit positions defined by front and rear piston inner shoulders, respectively |
| Abstract: A method and means of minimizing the effect of elastic valve recoil in impact applications, such as percussive drilling, where sliding spool valves used inside the percussive device are subject to poor positioning control due to elastic recoil effects experienced when the valve impacts a stroke limiting surface. The improved valve design reduces the reflected velocity of the valve by using either an energy damping material, or a valve assembly with internal damping built-in, to dissipate the compression stress wave produced during impact. |
| Use: Pneumatic hammer drill i.e. downhole hammer drill, for an impact application i.e. percussive drilling. Can also be used for a rock breaker, a water powered drill, a steam powered drill or a gas powered drill. |
| Advantage: The valve utilizes energy damping material or energy damping valve assembly so as to reduce rebound velocity, thus reducing the reflected velocity of the valve, and hence minimizing the effect of elastic valve recoil during impact applications. The valve includes an external shell filled with small particles or pellets/balls, so that the impact stress wave propagating through interior of the valve can be dissipated by interaction between the particles when an impact occurs. |
| Novelty: The drill has an air feed tube (14) supported along a central axis of a cylindrical outer casing (10). A reciprocating piston (12) includes a central bore (25) sized to fit closely over the feed tube that allows the piston to reciprocate forward and back along the feed tube. A reduced-impact sliding spool valve (30) is positioned over the feed tube inside the piston, and defines forward and rear limit stop positions defined by front and rear piston inner shoulders (34, 32), respectively. The valve comprises a thin metallic shell filled with particles or balls. |
| Filed: 4/16/2009 |
| Application Number: US2009424583A |
| Tech ID: SD 10955.0 |
| This invention was made with Government support under Contract No. DE-NA0003525 awarded by the United States Department of Energy/National Nuclear Security Administration. The Government has certain rights in the invention. |
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